Crucible furnace



July 20, 1943- c.- E. MILLIGAN CRUCIBLE URNACE Filed Oct. 1l. 1941 2 Sheets-Sheet l /N VEN Tof?.

l @M V07/ A 770/0/575.

July 20, 1943- c. E. MILLIGAN v 2,324,864

CRUC IBLE FURNACE Filed OC-t. ll, 1941 2 Sheets-Sheet 2 Patented'July'.ZlO','1943 'v Y. Electro Befractrics This'inventionrelates to'improvement's in cru:n

Ycassingnver the crucib1er so thatno'rotaryvor cible furnaces for. useimainly connection with the melting and refining of metals. *Y 7, Y When Crucible furnaces'areused' inconnection withv the meltngof' certain materials' or yingredievents, it is necess'aryztoikeep outsidefair as much as. possibleffrom contact 'With the contents .rot

'lthevcruciblfa l ,I l K u y f Itisalso Van object or this 'inventionftopro- Y Vdeaxcrucible of improved constru'cticnfjwhich the crucible inorderto prevent excessoxidation;Y`

of the contents.: Attempts Vhave heretofore been made to accomplish this result byl various meana For eXamp1e,-.in one typeof crucib1e'furnace,- acover is' provided forthe' furnace Vwhichy closes the top of' the* Crucible, the products of coni--` 1 bustion being discharged fromv the sides ofthe furnace',V4 Another typenf Crucible-iurnacev vhas` a'coVer-A'With azsmall vent vhole' therein over the crucib1e,v the coverbeing` spaced verticallyvfrom the "Crucible, topermit Y products of combustionA toV pass over the edgesof .theorucibleiiand'tojthe vent hoie. Bothof these' constructions. 'are ob-` jectionable in Ythat the covers 'must ybe removed, when the f Crucible' i is chargedfor '-'when ingredients are added, and When'the molten materialA must'be removed-from'thecrucble A I 1 One'o'f the objects of, this invention is top'rl vide' .a vCrucible furnace of improved construe!4 j tion, 'in which theginteriorfoffthe crucbleis Ya A crucible furnace-1of:` iniprcfwed"construction in "Whichvthe top .orjcover hasfan'openingfthereinj vwhich isarnpiy large enough to afford access openr fo'r lcharging and discharging; and in. which` the gasesof combustion arresov directed V,over the top'f the furnace asjto produce improved heat Ydistril'oution and better`:,th'erinai efficiency, f 1' i' 'Another',objectnofithis invention is. to' provide to the nteriorof the Crucible forr feeding 4mate-i furnace'and alsofto prevent' whirling 'of-the' gases whirling[motionV is imparted'to Ythe contentsfof v is so formed asvto cooperate-Withl Va'furnace so' as to produce as curtain fproducts o1"'clojx'n'busl`y VOther objects andfadvantages off this `invention' Y will bey apparent fro `the following' description andciaims; 1

I V.In the acconipanyi'ng'l drawings, Whichl's'how'by` `VentioniH Way of example several'embodimentsfof this iii-- *Figi 1 isaivertica central s'ectiofnalfelvation y.

01's a/crucibie Vfurnace embodying this invention'f Fig. 2 isa sectional plan-view thereof; on line Figs. 3 and y4 'are ffraglnen'tarykcentral*sectional Y furnaces' foftwolmodiiied'A constructions'f-f i substantially the entire top :ofzvtherrcrucible YisA rial' thereto drorfdischarging Vthernolte'n mai- 'terialtherefromg and iirwhichlmeansl are pro-A 'Vi'ded for. directinglthefproducts of combustionl over' the uppersurfacefof1t'iqie'fmolten-materialk ,in thelcruciblefin sucha-'gmanner'as tosubw" Y i e stanti'ally exclude air' from Contact with theicon.-

f tents'of the'crucible.

f A further :object of vthis irnzention fis-to provide cibler. fsuch aasfvtofravoid new, .or ygases` of com lined-with''any suitablerefractory 'composition bustier-1 .yiownwardlygtoward them tori-a1 the 55 fied construction@ j may -beapplied-'tolany s table; i

:outer '.cyimdricai `van liol 'and a bottom ali i Fig. 5' is vav bottomplan-vieW-ona; reduced sscalfe; y

of thetopforcover member of the furnace"atterrit` Amy Fig; 4. i

Fig. is a; fragmentary f sectionaifelzevatiren;

v'Myx'invention Y p K or- 'desired type.` of ecrucibleljfurnace; {an'd accompanying drawingsftheyffurnace s= ho-'e'vl'V 'i' as ofsuhstannany :cylindrical-isha@ both of; which` may: bevor' 'maar Va layerV ofinsuiating ima-termi 2 arranged 'ruim n omitted.' The side Wall'sfoiy the' furnacei may' be l5.LA 'l'l'V represents 'fthe-fcrucibiewliichv; may be made of any suitable or esird shape and -nifte--r Y Vria1,'and this crucible'preierabl Y suitable pedestai bioekforf ba'sjefia snppqftd byj l ,o .A f thebotto'n-rof theiurn'aeiand'ipreferabiy inade" A al cruciblexfurnace in'fWhichi-the rpassages for i x lproducts of combustion over' theitop of: the crun o Thezinteriofrof the'furnaee slilf ver bly cy l-nd-ricaii' and thecruoible pedestal?! 8 are' preferabilyI of circuar cross andlof' mattei;

rially smaller diameter than the inner diameter of the furnace, so as to form an annular space or combustion chamber in which flame and products of combustion may travel about the Crucible. The fuel and flamerby means of which the furnace is fired may be admitted to the annular combustion chamber between the crucible andvinner wall of the furnace in any suitable or desired'manner, and in the construction shown, the side wall of the furnace isprovided lo with an opening or burner hole thro-ugh which a fluid fuel Yburner may extend into Vthefurnace; f preferably in a substantiallytangential direcr tion. Thefurnace may Aalso be provided in the lower portion thereof with a slag hole 2|. A furnacerof any other suitable or desired con-A struction may be employed.

The furnace also includes a top wallor cover which `is preferably of annular shape and which' rests on top of thev furnace wall. This top orr covermay be of any suitable or desired-form, andv inv the ,Constructionshowm includes an., iron ring 24 and a ring 25,Y Figs. l and 2,.'of'refrac.- tory:l material which is bonded or otherwise'suit-` ably secured tothe lower face of the reinforcing l ring 24; andwhich'protectszthe ring 24 against damage from the flame or` products of combusftion. The ring 24 may, however, .be` omittedpif. desired. Thezcover may beheld in place on: the

furnace in4 anysui-table 'or ldesired manner, and

may merely rest by gravity on the topv wall of the furnace."` IntheV particular `Construction shown, the topmetalv ring 24 of the cover isprovided at intervals with outwardly thearm of vbracketsll'ofthe cover with brack-y ets 29 .arranged on the side wall'of the, furnace to securely hold the cover in place on Athe' `fur-l nace, AIt will -be noted that. the. coverzorylideof thefurnace is provided with a Vcentral holeor opening 30 `which isA approximately.. ofY the same In accordance 'providedfor protecting the `contents of thecrucible from damageor excessive oxidation, With.- out j renderinggthe contents. o fgthe 1 Crucible less accessible, and this is accomplished by "providing means for directing the flame .and products of Vvcombustion from the combustionjspace of` the. furnacel laterally across the top .ofthej Crucible ingsuchjagmanner .that the, air will jbef excluded `from uthe Crucible tov the maximum f'extent;f 1 AIt is alsodesirablefto,provide means Afor Vconducting the flameyand'products of Combustion across the top o fmthe crucibleeinsuch'a manner? that this flame and products of `Combustionwill notbe ldirectedgldownwardly toward the contents ofthe:

Y extending rarl'ns or brackets'Zl.I Clamping bolts 28 connect with this invention, means are,

"grooves in the cover.

Crucible. VThese passages may either be formed bynotching out one or more portions of the top of the Crucible or by providing corresponding grooves or recesses in the lower face of the cover or lid of the furnace or notching or recessing both the Crucible and the furnace top or cover.

In ,the particular construction shown in Figs. land 2, fthe'passages for the products of Cornb'u'stion are formed both by means of notches or recesses in :the upper edge of the Crucible and by In these figures, I provide inthe under or lower face of rthe Cover or furnace top a plurality of grooves or recesses V32 extending'outwardlyfrom'the Central'hole or apervpassages for the products of Combustion. If desired, thenotch or notches in the Crucible may be arrangedout of registration with the groove or grooves in the'cover. Between the grooves 32, the lower face of the cover is flat and in Contactwith or .in close proximityto the unnotched portions '3610i the Crucible. In the particular. construction shown, three grooves and cooperating-notches, are employed,Y which are unevenly spacedabout thefaxis ofA the furnace, but Vanyzdesired.'niunber of .notches and grooves mayfbelemployedand they may be arranged in any'desiredmanner about the periphery of the Crucible.V j, l 'r Inthe operation of the furnacedescribed, 'as- Vs'uming that-.the burner Vextending through the hole20 discharges` fuelandviiame substantially tangentially into the combustion space between the inner. wall. ofthe furnace andthe Crucible.

'this 'ameuwillheatf-the wall yof the-'Crucible 'I1 and will rise tothe upperpor'tion of the combustion space,l whereupon it will'l pass 'through'A the passages formed by the` notchesY 35 and vthe Crucible, since any heavier or-solidLparticles of mattercontained inthe products of 'combustionwould then be discharged into the crucible and contaminatethe material therein. It is also' very important that` the products offcombustion andA flame be `directed rcrosswise of 'gthegcrucible -in such` a mannerl as to Vavoid imparting any rotary motion te 'the molten contentsA Aof .the Crucible sincevsuch rotary vrnotijon'ofj the Crucible contentsisfvary:damagingv to the Crucible wall.:

-'lnvorderfto jaccornplishtheseresults; I have provided in the upper portion of thefurnace.; one or moreY arc-shaped discharge, passages through which. flame-and products of vcombustionv may pass from the combustion chamber. These ipas` SageseXtend horizontally. between; the lid or Cover of the furnace and the upper edge of the grooves 32 of the Cover or lid andvwill, consequently, pass in a substantially. radial and horizontal vdirection across the upperpart of the cru- Ciblelflhe flame Vand/or hot products of Combustion `in passing over the material in the Crucible will impart al portion 'of their heat by radiationrtozthe` materialin the Crucible and at the same timeftheflame. and'gases will'form acurtain-over the top of the zc'rucible, which will to 4a large extent excludeair fromY the Crucible, and

thus prevent excessive oxidation of the material inthe crucible. By means of thearrangem'ent described,v it will be noted that the flow' of products` of vCombustion `across the icrucible is substantially horizontal and finally upwardly, so that there'is no tendency ,ofthe flame orA combustion Vgasespto flow downwardly toward the contents ofthe crucible,.which downward Vflow .would re-4 sultin the Vthrowingout ofsolid or liquid pari ticles from the products of combustion into the crucible.. The construction described also has the advantage.tha'tfb'ecause of the large'size of the'hol'e'V or opening 30 in the coverof the furnace, thelfflameor Combustiongases will ow upwardly slowly, thusmaking Vit possible for themr t9 transmit a greater portion of the heat cona. :Crucible lit-is employedaoarleee j 3 theiireotonofinoternent of the-eases of come' tained. @been to the ontents of 'f the when@ v than Wouldbe possible if they Wereforced to flowy moreropidlyithrough a: Smaller holelor opening.

-j Goosefruontlv, the large hole .'30 not only facili.-v totes -theaohareing and discharging of .the-Crucible butfalsozincreasesfthethermal eiiiciency of InFi'gs.13, 6 `and 'lpthe furnace is provided with a-.topgor overfglkWh-ich maybe similarin conf Strootioaend :shape to that `shown in' Figsnl and' 2, exoeptathot'tho lower Surfaoelthereof .isY substantiallvat, the grooves orresses Shown. f te@ ln this furnace] in Figs-f1. :and .2Y being omit ovinaorie or more loo.itolifa or depressions .43. inthe upper. ed'ee' thereof, lof suoient size' to. Corry the products of oom',-

buston from the oombuStion-ohameer .across the 'rtopofftne erucible.:

-- Inj some cases, itmay-bedeSirable;tolemployfa A Crucible Without; the-notoires in .the upper edge Y thereQf -s that. the, ,f'u'u .capa-gay .or the Crucible. may ,b e; utilizedr Insuch ca se'rga construction maybeemplyedasgshownin Figs. 4 and 5,'inl .which the cover 5!) 'is .1provided with one or more. l groovesA or `restesses iii-formed on thelower sur- Ylace thereof', and in this constructiomthe cruc'ibleY 5:2 ist provided-with an'onnotohed-or plain upper edgar The groove-or grooves 5,-! inthe. @overprotion .acrossthe tor ofthe orooiolo-L.

vide forfthepossaeooithe/products. 'of folrlbus-v In ithe construction shown .in qligs. Vv3 to?, no., .particular preo-aution nood'beemployedin pleo.-

ine the Y oovernor. top of .the fornace. into .its on erative position, Whereas in Figs'. 1 and'2, it, may

desirable, tl'rat .the grooves, in; the covery lbe substantiallyin registration with;v orfin definite relation to the notchesin. the Crucible.` p

In they Narie-us construe-tions shown inFigs. V1

tof'i-rioiusiret notoires inthe. rl'ucible for tlc-,o i

grooves .in Athe cover `.are4irregularlyspaced from l Y' other.;leaviuaarelativolr large .uv-notched Vor ungroovedportf nLatone-sideot the furnace. l,

arrangement-Ytrillftendto ffoaese'tbe gases of-.combustion to. flow upwardlyv somewhat; .more

adiaoent to the, :1a-rater, unoothefl. or .oog-roofed' Y portion ofthe'ureaoe-So vthat While the furnace is `in operation, an operator may A.vrij-lativut`.difllf oultrfapproaoh the-forno@ for Charging 01 dS- .Y

charging the same While the burner is inoperation, if he approaches the furnace Tat portions Vthereof remote from the unnotched or ungro'ovedV f Y part ofv Athei largest `dimen'sion., -It is, however,

not necessarygthatttheifurnace be' so'constructed, 1 since any suitable arrangement of grooves or ,Y

notches about .thel periphery ofthe Crucible. may

.be employed. .Bywayofexample, there is shown n Y `inFig. 8, a Crucible of a different form having'a relativelylargeV number yofnotches 6| in the upper edge thereof,V which Yare spacedbetween av similarlnumberjof parts 62 Which'extend Y' upwardlyinto close proximity to the cover'. Thepassages for products of. combustion '.formed by notches in the Crucible 4and/or grooves 1 Vin the cover may vary inasizeY or cross sectional area, depending upon the amount; and type of l I fuel Which is being us'edfper unity of time. For

example, if'za furnaceV isV operated on" a very short cycle,flargeropenings will be required to accommodate the vrelatively large volume of combustion gases,than Vwhen a furnace is operatedl on a relatively 'long ,cycle, orin other Words,is-V

heated more gradually;

While the flame and productsyof combustion- Within the combustion chamber generally-travel I inta substantially helical or Vcirculanpath,Y yet` buStiQn-- when. tneypa-ssthrough the lo .so-eos formed by the grooveszr, notches isfmod dso that the. geweer@ siisohargod hrouehth the oruotblehove ex-seeerellr .radial-.idioot .Cofsefliiefitla 'Some furnaetooslitioneareltivelyflarge m1111-l met ,be

et? Refill? contents of rthe .trilspzere tot. tollera .efltlt molten metals. Y Y w ,Y 1 :In the usegof the furnace described,1tl!1e`,co ver detre@ to @ottenerne-tf at# te prof .the rurnaCe, sincethe hole pover lelie@ enough.. `so that or leather-gediendgttieoootents out; through 'tl-ifa. ,peeing fio. 'the' icularJ-lconstruction lo.- ,detti :et oiblolsino. theeeses Qoombustiorl. form. o, tur'- r Ye theol' @Hole weie Eurthermoraf by 1,11 the. relatrelr leraehoie oronenioei... has VYthe advantagethat#the gases discharged 50. through the passages over the curcible'may ow slowlythrough this large hole, and consequently,

remainV in proximity to the contents of the crucible for av somewhat'longer time, Yduring Ywhich theycan transmit a larger portion of their heat;

55 Yto the contents of the Crucible. `Sincethis heat the thermal eciencylof the Ycrucible:y

Y all partsof YVthe crucibles are exposedto substanftiallyV the same temperatures, ,thus avoiding the setting up of strains inthe'cru'cibles dueto dif- `ferences in temperatureof differentparts 'there of, as would result inrfurnaces in which the up-V per -ends'` of the'crucibles extend'above the fur- Wenas-7 motion yeneide not ob1e..,..ThiS alimentato-Sino@ agitation. or Y .hiding motion, Qi 'the .molten mutants" of! the Qloiblehevaefoorrosiro;effeote-iioorr theY .Crucible ''he'oorts Y ber. Cif passages mor. 'be aesirablawhile .under y, no heavy.

i eine; what is; undesirable sincero-treten. Ltal,eit'ftupon.

desoibedt this,

substantially; ex?, f l

he covenof the furnace. l

is transmitted direcnyfto the materiarin the Crucible and Adoes not'fhave to passY through l the? Wall ofi. thecrucible, it 'materially increases: n

-. :Furnaces constructed in accordance'with, my invention have. the further yadvantages that'the o crucibles areentirely Within the furnaces so that Y naces, By vforming the passages-for products of vcombustion in the .upper edgesof thecrucibles A Y j. or in 'the covers, manufacture ofthe crucibles is Y :facilitated and this also gives the'crucibles great-V er effective heights for corresponding` overall heights, so that the crucibles have' g'reatercapac-V ities for material to be melted than crucibles having'passages below theirl upper portions.

4I claim as myeinv'entioni: 1. A crucible furnace having anv outer substantially annular wall,a crucible arranged "within said wall to form therewith anY annular combiis# tion chamber,V a. cover for said furnace which closes the `upper end of saldcombustion chamber and which has .an opening therein which is sub# stantially coextensive with the" open' upper end cfr'the crucible, said' cruciblehavinga portion thereof of less'height measured to theupper edge Y of the crucible `than other portions and spaced Y.

from said cover toform a passage for products of combustion from said combustion chamber across theupper portion of said cruclble. i

2.v A crucible furnace having an outer substantially annular wall, a Crucible arranged lwithin .n saidwall to formrth'erewith an annular combustion chamber, a cover for said furnace which' closes the upper end of said combustion chamber and 'which has an opening therein which is sub- 1 stantially coextensive with the open u per end of thecrucible, said crucible having a notch formed in thefupper edge thereof and said 'cover having a radially extending groove' therein and extendingfrom said'combustion chamber to `said ber and which has an opening therein which is substantially coextensive with the open upper end of the Crucible, said crucible'having a notch formed in the upper edge thereof and'said cover' combustion having a radially Vextending groove therein andV extending from said combustion chamber said opening in said coverpsaidgroove' in said cover Y Y being farrangedrover said notch in saidcrucible to form therewith a passage through which productsvof combustion from said combustion cham` berilow in a substantially horizontal direction across the upperportion of said' CrucibleV toward the axis thereof. Y

4. A cruciblefurnace having an outer substantially annular wall, a crucible'arranged within saidA wall to form therewith an annular combustion chamber, a cover for said furnace'which closes the upper end of said combustion chamber and which has anopening therein which is substantially coextensive with the openupper end of the crucible, the upper edge of said crucible being provided at; intervals with notches and said cover being provided atr intervals with a plurality of grooves formedv in the'und'ersurface thereof and extending from the upper portion of said combustion chamber to'said openinggin said cover, said `notchesjand grooves forming a plurality'v of substantially horizontal passages between said cover and said crucible `for conductingA 'combustion gases from saidchamber in a substantially horizontal direction Aacross the upper portion of said crucible, 'the side walls 'of said passagesV acting tonguide Vthe products of across the upperportion of said crucible'.l "-f '5. A- crucible for use in a furnace havingVV al cover extending overrthe furnace and over the upperl edge of the crucible, 'said :Crucible being provided with a notch in the upper edgeVV thereof of materially `greater dimension ,circumferentially of the crucible than vertically thereof, for forming with the furnace'y cover ay passage through whichproducts of combustion may pass over thev top of thefcrucible inthe form ofV a curtain; I e

V6.. A Crucible for use 'in fa furnacehaving a cover. extending overV the furnace and over the upper edge of the' crucible,A saidr cruciblefbein'g provided with a plurality of notches in the upper edge portion thereof, each of said notches being of materially greater dimensioncircumferentially of the Crucible than Vertical1y,' said notches forming with the coverof the crucible apluralityl of passages through Which'products of 'combustion may flow substantially horizon-V of the Crucible.

CHESTER E. MILLIGAN. I 

